The Role of the X-linked Retinitis Pigmentosa Protein RP2 in Vesicle Traffic and Cilia Function

Primary cilia play a vital role as mechano- and environmental sensors. The photoreceptor outer segment is a highly modified and specialised sensory cilium that detects light. Diseases that affect cilia function (ciliopathies) have been identified as the underlying etiology of numerous genetic disorders such as renal cystic diseases and retinal degeneration. Many of the genes that cause ciliopathies encode functional or structural components of primary cilia or basal bodies. Recent evidence shows that the retinitis pigmentosa (RP) protein RP2 and the small GTPase Arl3 play important roles in cilia function by facilitating transport and docking of vesicles carrying proteins destined for the primary cilium. RP2 localises to the periciliary ridge, the basal body and Golgi complex of photoreceptors, as well as the primary cilium of renal cells. Two newly identified RP2 interaction partners, N-ethylmaleimide sensitive factor and polycystin 2 further support a role for RP2 in vesicle transport and cilia function.